1. Field of the Invention
The present invention relates to a leader tape, to a magnetic tape cartridge in which the cartridge case rotatably houses a reel with a magnetic tape wound up therearound along with the leader tape bonded thereto, and to a magnetic recording and reproduction method.
2. Description of the Invention
As magnetic tape cartridges used as recording media for external memory devices for computers and others, heretofore known are those of a type where a magnetic tape is wound up around one or more reels rotatably housed in the cartridge case. Since the magnetic tapes are used for data storage for computers and others and since important information is recorded therein, the cartridges are specifically so designed that they are free from a trouble of tape jamming and that a magnetic tape is not carelessly led out of them.
In a single reel-type cartridge, a leader member such as a leader pin or a leader block is fitted to the top end of the magnetic tape, via which the magnetic tape is led out of the cartridge; or a leader tape is bonded thereto, which is formed of a relatively hard plastic material and which has engage holes formed at the top end of the tape. For the cartridge of the type, a drive device is so constructed that the magnetic tape therein could be loaded/unloaded (draw out/wind up) while the leader member or the leader tape top end is held by the holder member on the side of a recording and reproduction device.
In the loading/unloading process as above where the magnetic tape is drawn out toward the side of the magnetic recording and reproduction device and its top end is wound up around the drive reel in the device, the top end of the magnetic tape is contacted with the tape guide and the magnetic head disposed along the tape-running route, while not accurately positioned relative to them, and in that condition, it is pulled and is therefore readily damaged. Accordingly, it is desirable that the top end of the magnetic tape is reinforced.
In addition, the reinforcement is also desirable in order to prevent the leader block level difference occurring in the drive reel from being embossed onto a data-recording magnetic tape to increase the dropouts in the tape. For this, a leader tape having a higher strength than that of a magnetic tape is bonded to the top end of the magnetic tape (e.g., see JP-A-2001-110164).
With the recent increase in the capacity of magnetic tape cartridges, the recording density of magnetic tapes is increasing, and drive makers are now toward increasing the in-plane recording density of magnetic tapes by reducing the recording wavelength so as to increase the recording density in the machine direction of tapes and further by reducing the recording track width so as to increase the recording density in the lateral direction thereof. With the increase in the recording density, the influence of the spacing between the magnetic layer and the magnetic head increases, and therefore, when magnetic tapes are deformed, then they cause dropouts and significantly increase error rates.
The leader block mentioned above is so designed that it may be housed in the recess formed in the core of a take-up reel, and when housed therein, a part of the leader block forms a part of the arc face of the core.
This is graphically illustrated. As in FIG. 4A, a leader block 40 is fitted into the recess 42 formed along the radial direction of the core 41, and, for example, in this condition, the end face 40a of the leader block 40 forms a part of the take-up face of the core 41. As illustrated, the end face 40a of the leader block 40 is curved like an arc in correspondence to the outer peripheral face of the core 41, in order to smoothly wind up the magnetic tape MT around it.
However, in such a related art tape drive, the end face 40a may protrude above the core 41, as in FIG. 4B, depending on the dimensional accuracy of the leader block 40 that constitutes a part of the take-up face, and it may form an unacceptable level difference in the take-up face of the core 41.
The level difference may cause folding or deformation of the leader tape LT, and, as in FIG. 4C, the folding and the deformation occur similarly also in the part of the magnetic tape MT which is wound up as the subsequent layers and which is to be a substantial recording region (this may be referred to as “leader block embossment”). The leader block embossment may cause a problem in that a suitable distance between the tape and the recording/reproducing head could not be ensured in the process of information recording/reproduction, and it may therefore cause recording failure and information loss.
If the time for which the tape is kept wound up around a take-up reel is short, then the leader block embossment would not cause the problems as above, but when the magnetic tape MT is kept wound up around the take-up reel and left as such for long, then the magnetic tape MT may often have a regular leader block embossment on the surface thereof, at a pitch of nearly the circumference length of the core 41.
Accordingly, it has become necessary to improve the leader tape. This phenomenon is more remarkable in a system where the line recording density is smaller. In a system where the difference between the recording track width and there production track width is over 17 μm, tape deformation to cause track shifting by a few μm or so may not result in the increase in dropouts, since the recording track width is much broader than the reproduction track width and therefore the tape may run on the recording track even after such a little tape deformation. However, in a magnetic recording and reproduction device where the difference between the recording track width and the reproduction track width is at most 16 μm, the track shifting owing to tape deformation becomes remarkable; and in a magnetic recording and reproduction device where the difference is at most 10 μm, it is substantially remarkable.